Abstract

Effective navigation requires planning extended routes to remembered goal locations. Hippocampal place cells have been proposed to have a role in navigational planning, but direct evidence has been lacking. Here we show that before goal-directed navigation in an open arena, the rat hippocampus generates brief sequences encoding spatial trajectories strongly biased to progress from the subject's current location to a known goal location. These sequences predict immediate future behaviour, even in cases in which the specific combination of start and goal locations is novel. These results indicate that hippocampal sequence events characterized previously in linearly constrained environments as 'replay' are also capable of supporting a goal-directed, trajectory-finding mechanism, which identifies important places and relevant behavioural paths, at specific times when memory retrieval is required, and in a manner that could be used to control subsequent navigational behaviour.

a, Vectorized trajectories (left) and average posterior probability sum (right) of all home-events for R1,D1, centered by rat’s physical location at time of event and rotated and scaled according to direction and distance to the previously rewarded RANDOM location. White circles: quantified regions. b, As a, for HOME. c–e, Across all rats, mean representation of quantified regions as in a–b. Event number displayed on bar. f, Normalized ratio of well/rat representation for c–e. P-values (Wilcoxon rank sum test): D1 HOME vs. Prev. RANDOM 4.4x10−16, HOME vs. Next RANDOM 9.9x10−3; D2 HOME vs. Prev. RANDOM 3.1x10−20, HOME vs. Next RANDOM 1.3x10−13.